1. Technical Field
The technical field relates generally to remote afterloading devices used to position radioactive treatment sourcewires within catheters inserted into patients to treat cancer or for use in conjunction with an angioplasty procedure, and, more particularly, to a manually operated afterloader.
2. Description of the Related Art
Radiation is used to treat cancer and other diseases of the body. Brachytherapy, is a general term for the radiation treatment of cancer at close distances inside the body. During brachytherapy, a radioactive source or sources are positioned in the area needing treatment. Angioplasty is a general term for opening a constriction in a blood vessel or artery. Radiation treatment has been found to be useful in preventing reclosure or restenosis of the constriction. Depending on the type of therapy, the radioactive sources are placed permanently inside the body during surgery, or transport tubes (treatment catheters) are placed in the body which are later temporarily loaded with radioactive sources via wires. This temporary afterloading of radioactive material involves a machine called an xe2x80x9cafterloaderxe2x80x9d that will load and unload the radioactive material into and from the transport tubes.
Afterloaders are devices generally used accurately advance and retract a flexible drive member containing a radioactive source over a specified distance for a specified time period. An afterloader generally consists of a flexible simulation drive member, a flexible drive member containing a radioactive element or sourcewire, computer controllers and motorized drive mechanisms to operate both types of flexible members, a shielding safe for the radioactive element, an internal timer, and, in brachytherapy, an exit port attached to a rotating wheel that allows multiple transport tubes (previously placed into the patient) to be hooked up to the device at the same time. The afterloader usually sends out the simulation member to check the patency of the transport tube without subjecting the patient to undue radiation exposure, and then sends out the radioactive element. After the treatment is performed in the first transport tube, the afterloader retracts the source into the shielding safe inside the afterloader, a wheel turns and aligns a slot containing the second transport tube to an exit port. The afterloader then repeats its function sending and retracting the simulation member and radioactive member through this second tube. The procedure is repeated until the function is carried out through all the specified transport tubes. Since the afterloaders use a fixed, short length radioactive source, the afterloaders must multi-step this source many times inside each transport tube to cover the diseased area.
The current remote afterloaders on the market, initially designed for use in brachytherapy, are particularly complicated.
Limiting factors of prior art treatment afterloaders are the physical size and amount of equipment necessary to operate a remote afterloader. In many treatment facilities, there is not enough room for this amount and size of equipment.
When used with a sourcewire to treat a stenosis or constriction of an artery, an afterloader need not be so complex as to support multiple transport tubes or computer controlled indexing features.
Thus, there exists a need for a simple, compact, portable, self-contained afterloader for use in conjunction with, or after, an angioplasty procedure to provide radiation treatment of a vessel in order to prevent restenosis, i.e., reclosure.
A manually operable afterloader is provided for use with a radioactive sourcewire having a relatively short radioactive portion and a relatively long nonradioactive portion. The afterloader generally includes a base plate having a sourcewire reel rotatably mounted thereon. The sourcewire reel includes a circumferential groove which is configured to receive the nonradioactive portion of the sourcewire. A shield capsule or safe is also mounted to the base plate and includes a passageway therethrough for receipt of the radioactive portion of the sourcewire. Preferably, the pathway through the shield capsule is nonlinear so as to prevent inadvertent escape of radiation from the capsule.
A guide tube is provided between the sourcewire reel and the pathway of the shield capsule. Adjustment structure or an adjustment clamp is provided about the guide tube to properly align one end of the guide tube with tangent of the sourcewire reel so as to receive the sourcewire from the reel.
The manually operable afterloader further includes a cranking mechanism which is operably engagable with the sourcewire reel. The cranking mechanism generally includes a crank wheel having a crank handle attached thereto. The crank wheel is connected to a drive shaft which in turn is connected to one side of a slip clutch. The sourcewire reel is mounted on a second shaft which is connected to the opposed side of the slip clutch. Thus, rotation of the crank wheel by a manipulation of the crank handle rotates the respective drive shafts through the clutch to drive the sourcewire on and off the sourcewire reel. Preferably, the slip clutch is designed to slip at a pressure of approximately two pounds to limit the driving or retraction forces provided to the sourcewire.
Further, as a safety mechanism, crank handle is pivotally mounted to the crank wheel such that when the crank handle is in a retracted position, it engages a mechanical or frictional safety thereby preventing inadvertent rotation of the crank wheel and thus the sourcewire reel. Further, a releasable braking mechanism may be provided to limit rotation of the sourcewire reel to an initial predetermined amount and, upon release of the braking mechanism, allow further rotation of the sourcewire reel.
The sourcewire reel includes a circumferential groove for receipt of the nonradioactive sourcewire and further includes a larger width or diameter groove above the sourcewire groove for receipt of a flexible cable or belt. The flexible belt is provided to restrain the sourcewire within the groove as the reel is rotated so that the sourcewire does not flex or pop out of the groove as it encounters resistive forces going to a treatment catheter. A takeup assembly is provided to control movement of the flexible cable and provide predetermined rates of tension on the cable so as to restrain the sourcewire within its respective groove. Preferably, the takeup assembly includes a first pulley fixedly mounted to the base and adjacent the sourcewire and a floating pulley floatingly mounted and biased by spring tension. An adjustment mechanism is provided to adjust the tension the flexible pulley provides about the belt relative to the fixed pulley.